In vitro stimulation of naive CD4 T cells with basophils promotes induction of Th2 type response. A total of 5 × 105 5C.C7 CD4 T cells specific for PCC peptide were cultured with 1 μM peptide and 5 × 104 splenic CD11c+ dendritic cells in the presence or absence of basophils for 3 days. Cells were restimulated on platebound antibodies for intracellular cytokine expression. (A) A total of 2 × 104 basophils isolated from the liver of IL-3–treated mice in vivo were added in the cultures. Proportions of IL-4– and IFNγ–producing cells are shown. (B) CFSE profiles of CD4 T cells cocultured with or without basophils were determined. (C) Different numbers of basophils (none, 200, 2000, and 20 000) obtained from indicated tissues (liver, spleen, or bone marrow) were added in the coculture. Graphs indicate percentage of cytokine-producing CD4 T cells. The means ± SD of 2 independent experiments are shown. (D) Indicated numbers of in vitro–generated bone marrow–derived basophils and mast cells were cocultured, and cytokine production was determined following restimulation. (E) Naive 5C.C7 CD4 T cells were stimulated described for panel A in the presence of IL-12 with or without 2 × 104 basophils, and cytokine production was determined. (F) Th1 cells generated in vitro (by stimulation with 10 ng/mL IL-12, 10 μg/mL anti–IL-4) were restimulated with antigen in the presence or absence of 2 × 104 basophils. All the experiments were repeated more than 3 times with similar results.
